Problem: A box contains $9$ red balls, $4$ green balls, and $3$ blue balls. If a ball is randomly chosen, what is the probability that it is not blue?
Explanation: There are $9 + 4 + 3 = 16$ balls in the box. There are $3$ blue balls. That means $16 - 3 = 13$ are not blue. The probability is $ \frac{13}{16}$.